Liquid propelling device



July 21, 1964 J. LISTON LIQUID PROPELLING DEVICE Filed Feb. 5. 1962 INVENTOR. J55PH A/sro/V,

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United States Patent 3,141,439 LIQUID PROPELLING DEVICE Joseph Liston, 900 Robinson St., Lafayette, Ind. Filed Feb. 5, 1962, Ser. No. 171,131 4 Claims. (Cl. 11516) This invention relates to devices which, although not necessarily limited to such employment, are especially suited for use in propelling boats, especially small boats, by ejecting a high-velocity water jet rearwardly and at or slightly above the Water level. The thrust exerted by such a jet is given by the equation:

where T=thrust in lbs.

G weight rate of flow of ejected water in lbs. per sec. g gravitational constant w velocity of the jet, relative to the boat, in ft. per sec. V=boat velocity in ft. per sec.

The expression (w-V) in the above equation, which represents the rearward velocity of the jet in space, is an indirect measure of propulsive efiiciency, such efiiciency increasing with decreases in the value of that expression, as is well recognized. It follows therefore, always bearing in mind that the jet velocity, w, must exceed the boat velocity, V, that a jet propulsion device which ejects relatively large quantities of water at relatively low velocity is more efl'lcient than one which produces the same thrust by ejecting smaller quantities of water at higher velocities. However, if the pumping and jet-forming equipment are of conventional form, the former type of device requires larger and heavier pumping equipment than does the latter; and in many instances, notably in the case of small boats, space and weight limitations prohibt the use of the more eflicient type of jet propulsion device.

This invention therefore has for an object the production of a device, particularly suited for use as a jet propulsion device for boats, which, although embodying relatively small, lightweight pumping equipment, will nevertheless be capable of discharging liquid at a relatively high volume flow-rate but at a relatively low velocity. Another object of the invention is to produce a jet propulsion device, preferably of outboard type, which can be adjusted to provide best eificiency either for boat-hulls having different velocity-thrust ratios or for different speeds of the same boat.

In accordance with the principal feature of the invention, as embodied, for example, in a propulsion device for boats, the water inducted into the device is divided into first and second portions and the first portion is led to a pump characterized by a relatively high ejection velocity. The high velocity stream discharged from the pump is introduced into the second portion of the inducted water in such a manner as to create an ejector action which will accelerate such second portion, and the recombined portions are ejected as the boat-propelling jet. Conveniently, the propulsion device includes a duct having a forwardly directed inlet opening below water level and a rearwardly directed outlet nozzle located at least largely above water level, and the division of inducted water into the aforesaid first and second portions is effected by a vane disposed in the duct and adjustable to vary the proportion of inducted water directed into the pump. An outboard device embodying the invention may have the duct at the lower end of the conventional tubular frame member and may employ a vertical-axis centrifugal pump disposed in the upper wall of the duct and driven through a shaft extending upwardly through the tubular frame to a motor at the upper end thereof.

Further objects and features of the invention will become apparent from the following more detailed description and from the accompanying drawing, in which:

FIG. 1 is a side elevation of a jet-propulsion device of outboard type; and

FIG. 2 is a vertical section, on an enlarged scale, illustrating details of construction.

The device illustrated in FIG. 1 resembles a conventional outboard motor in having a tubular frame 10 adapted, through a clamp 11, to be mounted on the tran- $0111 of a boat. As is common in outboard motors, the frame is rotatable about a vertical axis for steering purposes under control of a handle 12 and is pivoted to the clamp on a horizontal axis as indicated at 13. Further resembling a conventional outboard motor, the device of FIG. 1 embodies a driving engine or other power-source 14 mounted at the upper end of the tubular frame 10. The device differs from the conventional outboard motor, however, in that jet-forming means, rather than a propeller, is provided at the lower end of the frame 10.

The jet-forming means shown in the drawing comprises a duct, designated in its entirety by the reference numeral 16, rigid with the tubular frame 16. The duct, in vertical section, possesses the form of an ogee curve and has a forwardly directed inlet opening 17 located below water level and desirably provided with a screen or grid 18. The rear portion of the duct is formed as a discharge nozzle 19 disposed to discharge rearwardly and at least in large part above the water level.

The upper wall of the duct 16 includes the housing of a centrifugal pump, and for that purpose is provided with a downwardly opening cavity which receives an impeller 21 secured to the lower end of a shaft 22 extending upwardly through the tubular frame 10 for connection to the power-source 14. The cavity in the upper wall of the duct 16 includes a volute 23 discharging into a rearwardly directed outlet 24 located within the longitudinal limits of the duct and preferably coaxial with the outlet nozzle 19.

Pivotally mounted on a horizontal axis at the rear of the opening into the pump housing is a vane 25 which projects in a general forward direction within the duct 16 toward the inlet opening 17. As will be apparent, by adjusting the position of the vane 25 about its axis of pivotal mounting, more or less of the water entering the opening 17 can be directed into the pump housing. Desirably, the vane 25 is rigidly attached to a shaft 26 which extends outwardly through at least one wall of the duct 16 to permit adjustment of the vane While the power-source 14 may take any desired form I prefer that it be a reversible gas turbine having a bladed rotor 30 secured to the upper end of the shaft 22. An appropriate form of turbine for use in the present invention is shown in my prior Patent No. 3,000,611, granted September 19, 1961.

When a boat equipped with my propulsion device is moving forwardly at any reasonable speed, the duct 16 will be filled with water flowing upwardly and rearwardly. Such upward and rearward movement of the water is due jointly to the ejector action of the water discharged at high velocity from the pump outlet 24 and to the ram effect existing at the duct inlet 17 as a result of the boats forward motion. As will be obvious, the water expelled from the outlet opening 24 will be retarded as it mixes with and accelerates the water which bypasses the pump, and the jet expelled from the nozzle 18 will therefore have a velocity substantially lower than that expelled from the outlet 24, but the volume rate of water delivery from the jet nozzle 18 will be substantially greater than that of the water expelled from the pump-outlet 24. As noted above, by reducing the high velocity of the water expelled from the pump outlet opening and employing the energy represented by that velocity-loss to augment the volume flow-rate, I have increased the propulsive efficiency,

The proportionate quantity of water directed intothe pump is controlled by adjustment of the vane 25. Lowering of the vane will increase the proportionate quantity of water passing through the pump and, if other conditions remain the same, will increase both the velocity of the jet ejected from the nozzle 19 and the thrust created by such jet. Conversely, raising of the vane will decrease flow through the passage and will also decrease jet velocity and thrust. Maximum efiiciency is attained when the vane 25 is so adjusted that the water ejected from the jet nozzle 18 will have the lowest velocity capable of producing the thrust required to propel the boat at the desired speed.

It is to be understood that the vane 25 need act only as a water-deflector rather than as a valve. It is not necessary that in the fully depressed position of the vane it direct into the pump all water entering the inlet opening 17, and it would, of course, be undesirable for the vane 25, in its uppermost position, to prevent ingress of water to the pump.

The adjustment of the vane 25 may be controlled in any desired manner. Where the boat, under normal operating conditions, will operate at a fixed speed, the vane may be held in a fixed position of adjustment which, for the particular thrust-velocity relationship of the boat hull, will give maximum eificiency at such fixed speed. On the other hand, if the boat is to operate over a wide speed range, and if optimum efficiency at each speed is desired, the vane 25 may be adjusted with regard to the speed, as by operably connecting it to the speed-controlling mechanism of the power source. If the power source is a turbine of the type set forth in my prior patent above mentioned, in which the flow of gas to the turbine is controlled by adjustable vanes in the inlet passage, the vane 25 may be operated by the same mechanism which controls the setting of the turbine-vanes.

In the particular embodiment herein shown and described, the pump-outlet 24 is located above the outside water-level, and will therefore be incapable of exerting any ejector effect promoting flow of water bypassing the pump until after the boat has attained, under the reaction of the jet expelled from the pump-outlet, a speed such that the ram effect at the inlet 17 will result in submergence of the pump outlet. Attainment of that boatspeed may be expedited by lowering the vane 25 to increase the proportionate quantity of water directed into the pump. Of course, if the pump-outlet is located in a portion of the duct which is below the outside water level, as is within the purview of my invention, it will not be necessary that the boat attain any minimum speed before the ejector action begins.

In addition to making possible increases in propulsive etficiency, a boat-propelling device in accordance with my invention has other advantages. One such additional advantage lies in the possibility of obtaining a relatively low jet velocity with a pump which operates at relatively high rotational speed and which may therefore be directly connected to a high-speed power source, such as a turbine, without any interposed speed-reducing gearing, Further, since only a part of the water conducting the jet flows through the pump, the effect of pump losses on overall efficiency is reduced and it becomes practicable to use relatively small pump impellers which can operate at turbine speeds without creating undue pressure rise or friction losses. The two advantages last mentioned are significant not only in jet propulsion but also in any situation where it may be desired to employ a relatively small, high velocity pump to move liquid at a relatively high volume flow-rate but at relatively low velocity.

I claim as my invention:

1. A boat-propelling device of the water-jet type, comprising a duct having a water-inlet opening at its forward end and terminating at its rear end in a jet-discharging nozzle, a pump having an inlet communicating with said duct intermediate its length and an outlet located in the duct and directed rearwardly whereby water impelled from the outlet will exert an ejector eifect promoting rearward flow of water surrounding the outlet, and a deflector mounted within said duct to direct into the pump a portion of the water entering the duct while permitting another portion of such water to bypass the pump to become subject to said ejector effect, said deflector being adjustable to vary the proportion between water respectively entering and bypassing the pump.

2. In a boat, a water duct having an inlet below the Water line and terminating in a rearwardly directed jetdischarging nozzle located at least in part above the water line, a second nozzle of smaller diameter than said duct, located therein, and directed rearwardly, a pump discharging water through said second nozzle to create an ejector effect on water surrounding the second nozzle and promoting fiow of such water to and through the jet-discharging nozzle whereby tocause the ejection from the latter nozzle of a boat-propelling jet having a velocity substantially less and a volume flow-rate substantially greater than those of the water discharged from said second nozzle, and an adjustable water-deflecting means for varying the proportion of jet-forming water that passes through the pump.

3. A boat according to claim 2 with the addition of means for driving said pump, means for varying the speed of said driving means, and means for jointly controlling said speed-varying means and said adjustable means.

4. An outboard boat-propelling device of the waterjet type comprising a vertically extending frame provided at its lower end with a generally horizontal duct having an inlet opening at one end and at the other end a jetdischarging nozzle disposed above the inlet opening, means for securing said frame to a boat-transom with the duct inlet below and said nozzle at least in part above the Water line, said frame being pivotally connected to said means on a vertical axis to permit varying the direction of the jet discharged from said nozzle, said duct having a pump inlet opening in its upper wall, a second nozzle of smaller diameter than said duct, located therein, and disposed to discharge in the direction of fiow therethrough, a centrifugal pump receiving water through said pump inlet opening and discharging through said second nozzle to create an ejector effect on water surrounding the second nozzle and promoting flow of such water to and through said jet-forming nozzle, a generally vertical shaft rotatably mounted in said frame, and means at the upper end of said frame for driving said shaft, said pump including an impeller fixed on the lower end of said shaft, and adjustable means for deflecting into the pump inlet opening a variable proportion of the water entering the duct.

References Cited in the file of this patent UNITED STATES PATENTS 1,418,921 Handley lune 6, 1922 2,412,825 McCollum Dec. 17, 1946 2,943,593 Megert July 5, 1960 3,019,600 Peek Feb. 6, 1962 3,082,732 Stallman Mar. 26, 1963 FOREIGN PATENTS 243,957 Switzerland Feb. 17, 1947 716,381 Great Britain Oct. 6, 1954 

1. A BOAT-PROPELLING DEVICE OF THE WATER-JET TYPE, COMPRISING A DUCT HAVING A WATER-INLET OPENING AT ITS FORWARD END AND TERMINATING AT ITS REAR END IN A JET-DISCHARGING NOZZLE, A PUMP HAVING AN INLET COMMUNICATING WITH SAID DUCT INTERMEDIATE ITS LENGTH AND AN OUTLET LOCATED IN THE DUCT AND DIRECTED REARWARDLY WHEREBY WATER IMPELLED FROM THE OUTLET WILL EXERT AN EJECTOR EFFECT PROMOTING REARWARD FLOW OF WATER SURROUNDING THE OUTLET, AND A DEFLECTOR MOUNTED WITHIN SAID DUCT TO DIRECT INTO THE PUMP A PORTION OF THE WATER ENTERING THE DUCT WHILE PERMITTING ANOTHER PORTION OF SUCH WATER TO BYPASS THE PUMP TO BECOME SUBJECT TO SAID EJECTOR EFFECT, SAID DEFLECTOR BEING ADJUSTABLE TO VARY THE PROPORTION BETWEEN WATER RESPECTIVELY ENTERING AND BYPASSING THE PUMP.
 4. AN OUTBOARD BOAT-PROPELLING DEVICE OF THE WATERJET TYPE COMPRISING A VERTICALLY EXTENDING FRAME PROVIDED AT ITS LOWER END WITH A GENERALLY HORIZONTAL DUCT HAVING AN INLET OPENING AT ONE END AND AT THE OTHER END A JETDISCHARGING NOZZLE DISPOSED ABOVE THE INLET OPENING MEANS FOR SECURING SAID FRAME TO A BOAT-TRANSOM WITH THE DUCT INLET BELOW AND SAID NOZZLE AT LEAST IN PART ABOVE THE WATER LINE, SAID FRAME BEING PIVOTALLY CONNECTED TO SAID MEANS ON A VERTICAL AXIS TO PERMIT VARYING THE DIRECTION OF THE JET DISCHARGED FROM SAID NOZZLE, SAID DUCT HAVING A PUMP INLET OPENING IN ITS UPPER WALL, A SECOND NOZZLE OF SMALLER DIAMETER THAN SAID DUCT, LOCATED THEREIN, AND DISPOSED TO DISCHARGE IN THE DIRECTION OF FLOW THERETHROUGH, A CENTRIFUGAL PUMP RECEIVING WATER THROUGH SAID PUMP INLET OPENING AND DISCHARGING THROUGH SAID SECOND NOZZLE TO CREATE AN EJECTOR EFFECT ON WATER SURROUNDING THE SECOND NOZZLE AND PROMOTING FLOW OF SUCH WATER TO AND THROUGH SAID JET-FORMING NOZZLE, A GENERALLY VERTICAL SHAFT ROTATABLY MOUNTED IN SAID FRAME, AND MEANS AT THE UPPER END OF SAID FRAME FOR DRIVING SAID SHAFT, SAID PUMP INCLUDING AN IMPELLER FIXED ON THE LOWER END OF SAID SHAFT, AND ADJUSTABLE MEANS FOR DEFLECTING INTO THE PUMP INLET OPENING A VARIABLE PROPORTION OF THE WATER ENTERING THE DUCT. 